Section 3 Cast Iron Smelting

#### **Chapter 5**

## Evaluation of Metallurgical Quality of Cast Iron Using Quality Criteria

*Peter Futas and Alena Pribulova*

#### **Abstract**

The metallurgical quality of the produced cast iron is related to its chemical composition (mainly the content of C, Si, Mn, P, and S), or other monitored elements—alloying elements (Cr, Ni, Cu, … ), in some cases showing elements (Pb, Sn, As, Sb, … ). The chemical composition of cast iron is determined by the degree of saturation (Sc) or carbon equivalent (CE). Other factors influencing the quality of cast iron are the metallurgical conditions of production (melting and treatment) of cast iron and the rate of solidification in the mold. The mechanical properties of cast iron (Rm, HB, and E0) are closely related to its chemical composition. In addition to this common evaluation of cast iron, other quality criteria of gray cast iron are also used in practice. This is a comparison of the mechanical properties of the produced gray cast iron with the optimal values determined for the same degree of saturation (Sc). This chapter concerns assessments of the metallurgical quality of gray cast iron and the results of operational melting of synthetic gray cast iron with different charge compositions in the Slovak Foundry and its analysis.

**Keywords:** metallurgy, quality criteria, cast iron, properties, steel scrap

#### **1. Introduction**

Cast irons are alloys of iron, carbon, silicon, manganese, and other elements, while carbon is excluded in the form of graphite or is bound as carbide Fe3C or carbide of another element. The carbon content exceeds the value of the maximum solubility of carbon in austenite, that is, C > 2.06% without the influence of other elements. Crystallizes according to the stable Fe–C or metastable Fe–Fe3C diagram, or during solidification and cooling using both systems (**Figure 1**) [1].

Gray cast iron is called gray because of the gray color on the fracture surface. It contains 1.5–4.3% C and 0.3–5% Si plus Mn, S, and P. It is brittle with low tensile strength but has good foundry properties.

The structure of cast iron is characterized by randomly oriented graphite flakes (**Figure 2**) [2]. The more sharp-edged the graphite formations are, the greater the notch effect, which reduces the plasticity of cast iron and increases brittleness.

The structure of gray cast iron usually has three phases: ferrite, pearlite, or martensite. The carbon content in the metal matrix exceeds 1%. It contains graphite in the form of three-dimensional structures, which have the shape of flakes on the metallographic surface. Their distribution and shape largely influence the properties of the

**Figure 1.** *Fe-Fe3C phase diagram [1].*

material. The best gray cast irons have a metal matrix with graphite flakes of varying size and uniform distribution.

The chemical composition of gray cast iron should be chosen to ensure the following:


The structure of the metal matrix affects the properties as follows:


Besides carbon, silicon is the most important element in cast iron. During solidification, it significantly supports graphitization, and during the transformation of austenite, it supports the formation of ferrite.

Gray cast iron is a widely used material in the automotive industry for engine blocks, brake discs, brake drums, and covers. It has good machinability with excellent wear resistance and excellent vibration damping. Thanks to its physical properties, it is preferred by designers and enables the production of castings with excellent specific properties, especially heat and fire resistant, abrasion resistant, and castings with special physical properties [3]. Its disadvantage is its fragility and relatively large dispersion of properties, especially mechanical ones, even with the same chemical composition. Solving this phenomenon requires excellent metallurgical and technological knowledge [4].

The worldwide trend of gray iron shares 54.4% (51,190,987 tons in 2021) [5].

#### **2. Quality evaluation of gray iron**

The quality of gray cast iron, usually expressed by values of mechanical properties (Rm, HB, and E0), is closely related to its chemical composition (content of C, Si, Mn, P, and S) eventually other monitored elements—alloying elements (Cr, Ni, Cu, … ), in some cases, pollutants (Pb, Sn, As, Sb, … ) [6].

From a chemical point of view, gray cast iron is evaluated from the three main categories [7]:

	- The optimum ratio between manganese and sulfur for a FeS-free structure and maximum amount of ferrite is [8]:

$$\text{\textquotedblleft}\text{\textquotedblright}\mathbf{n} = \mathbf{1}.\mathsf{\textquotedblleft}\mathbf{s}(\mathsf{\textquotedblleft}\mathbf{S}) + \mathbf{0}.\mathbf{1}\mathbf{S}$$

Other minor elements, such as aluminum, antimony, arsenic, bismuth, lead, magnesium, cerium, and calcium, can significantly alter both the graphite morphology and the microstructure of the matrix [9, 10].

3.*The trace elements:* Many other elements are utilized in limited amounts to affect the nature and properties of gray iron. Although some are not intentional, they do have a measurable effect on the gray cast iron. Some promote pearlite, such as tin, while others compact graphite and increase strength, such as nitrogen [11, 12].

The chemical composition is simply determined by the carbon equivalent (CE) or degree of saturation (Sc) [13].

#### **2.1 Carbon equivalent**

It takes the influence of the accompanying elements equal to the effect of the carbon into account and provides information on the composition relative to the eutectic composition in analogy to the degree of saturation, that is, it expresses the equivalent carbon content with respect to the iron-carbon binary system [6]:

$$\text{CE} = \text{C} + \frac{\text{Si} + P}{\text{3}} \tag{1}$$

In eutectic compositions, CE equals 4.3%; the following relationships exist between the degree of saturation and the carbon equivalent CE, mainly used in the Anglo-American countries [6]:

$$\text{Sc} = \frac{\text{C}}{4.23 - \text{CE} + \text{C}} \tag{2}$$

$$\text{CE} = 4.3 + C \left( 1 - \frac{1}{\text{Sc}} \right) \tag{3}$$

In all formulas, C is to be replaced with the total carbon content.

#### **2.2 Degree of saturation**

It indicates the ratio between the total carbon content of the melt and the carbon content of the eutectic composition. According to Eq. (4), it is under consideration of the influence of accompanying elements on the shifting of the eutectic point [6]:

$$\text{Sc} = \frac{\text{C}}{4.26 - \frac{1}{3}(\text{Si} + P)} \tag{4}$$

If other accompanying elements in the iron or alloy components are also considered, this results in the following exact formula Eq. (5) [6]:

$$\text{Sc} = \frac{\text{C}}{4.26 - 0.31. \text{Si} - 0.27P - 0.4S - 0.074. Cu} + \text{0.063.} \text{Cr} + \text{0.02.Mn} \tag{5}$$

*Evaluation of Metallurgical Quality of Cast Iron Using Quality Criteria DOI: http://dx.doi.org/10.5772/intechopen.107291*

A degree of saturation Sc = 1.0 means that the iron corresponds exactly to the eutectic composition.

Degrees of saturation above 1.0 have hypereutectic cast iron and thus result in the structural formations of cast iron to be expected under consideration of the relevant wall thicknesses. In the chemical composition of flake graphite cast iron, carbon has the strongest influence on the strength.

The lower the carbon content and the degree of saturation, the greater the strength because less graphite and more primary dendrites are present in the structure. Manganese, phosphorous, and sulfur in the usual contents have only a minor influence on tensile strength. Inoculation treatment results in an increase in the number of eutectic cells and thus in greater strength. The so-called Sipp diagram (**Figure 3**) [14], illustrates the correlations with regard to the material structure and the Heller-Jungbluth diagram (**Figure 4**) [14], those with regard to the tensile strength.

The degree of saturation can also be used for the approximate calculation of the tensile strength of gray cast iron depending on the wall thickness. According to Eq. (6) [6]:

Normal tensile strength Rm MPa ð Þ¼ 1000–800 Sc for the standard 30 mm test bar ð Þ

(6)

**Figure 3.** *Relation between the degree of saturation and the basic structure [14].*

**Figure 4.** *Relation between the degree of saturation and the tensile strength of flake graphite cast iron [14].*

The quotient of measured tensile strength and calculated normal tensile strength indicate the so-called degree of normality, an important quality parameter of the flake graphite cast iron.

There is a correlation between the degree of saturation and the carbon equivalent.

For most applications, a gray, pearlitic cast iron with a degree of saturation of approximately 0.85 to 0.95 for wall thicknesses of around 15 mm is preferred, with a carbon content of approximately 3.1 to 3.3% and a silicone content of 1.5 to 1.8%. As a general rule, the Si/C proportion for a given degree of saturation should be adjusted to a possibly high value.

They are used in quality criteria of gray iron in engineering practice, in addition to ordinary quality evaluation of cast iron, that is, determination of Rm and HB, eventually chemical composition or other required properties. This is a comparison of the mechanical properties of gray iron produced with optimal values determined for the same degree of saturation.

#### **2.3 Regression equations for calculation of mechanical properties**

Statistical methods (regression equations with multiple correlations) determine the quantitative relationship among the chemical compositions (basic, if necessary, accompanied by other observed items), or the degree of saturation or carbon equivalent CE and strength and toughness of gray cast iron, in some cases modulus of elasticity E0.

The most used equations to calculate the mechanical properties of pearlitic gray iron from its chemical composition are [6, 14]:

$$\text{Rm} = 786.5 \text{--} 150\text{\%C-47\%Si} + 45\text{\%Mn} + 219\text{\%S; variation s} = 25 \text{ MPa} \tag{7}$$

$$\text{HB} = 444 \text{--} 71.89 \text{€} \text{C-} 13.99 \text{€} \text{Si} + 219 \text{Mn} + 170 \text{\#} \text{S}; \text{variation } \text{s} = 12.4 \text{€} \tag{8}$$

$$\mathbf{E}\_0 = \mathbf{313.175} \mathbf{-449.01496C} - \mathbf{1408294} \mathbf{Si}; \text{variation } \mathbf{s} = \mathbf{6760 MPa} \tag{9}$$

The most appropriate procedure is to calculate the regression equation for its own foundry (i.e., for the specific conditions).

#### **2.4 The quality criteria**

*The degree of maturity of cast iron RG* specifies the level of quality of gray iron production compared with the optimal, determined by calculation, value of Sc, respectively, by correlation Eq. (6):

$$RG = \frac{Rm\_{measured}}{Rm\_{calculated}} \bullet 100\% \tag{10}$$

where Rmcalculated = 1000–800 Sc It also determines *the relative hardness RH* [6]*:*

$$RH = \frac{HB\_{measured}}{HB\_{calculated}} \bullet 100\,\% \tag{11}$$

where HBcalculated = 100 + 0.44 Rmmeasured.

A value above 100% means a high quality of gray iron.

*The quality number GZ* or quality factor is obtained by dividing the RG/RH or by Rm/HB—measured values. Qualitative gray iron has high strength at low hardness.

#### **3. Evaluation of quality of gray iron in a particular foundry**

In the operational, conditions of foundry in Slovakia have analyzed 122 melts of gray iron EN-GJL-250 with different charges. The steel scrap rate was 77.82% and the return material was 22.18%. In the foundry, also one melt with a 100% rate of the steel scrap in the charge was realized (synthetic gray iron).

These melts were realized in two low-frequency induction furnaces "Siemens" with the following parameters:


The cast iron was by the bar gauge treated FeSi75. The temperature of the superheated melt was between 1420 and 1440°C.

Next samples were a cast from the melts:


The samples for metallographic analysis were taken from the test bars and prepared in a standard manner.

The hardness was measured with the durometer HPO 3000 (terms: 10/3000/10), that is, the diameter of the ball was 10 mm, strength duration was 3000 N, and period of load was 10 sec.

Tensile strength was measured on test bars (Ø30 mm) on the universal crackle machine ZWICK.

The statistical results of the chemical composition and measured mechanical properties are documented in **Table 1**.

The stress results of gray iron (EN1561) show small dispersion of Rm (260– 285 MPa), the average value of Rm = 274 MPa, which confirms the uniformity of production. The decrease of Rm by an increase of Sc is slight (**Figure 5**).

For the melt with 100% steel scrap, the charge hardness that was greater at approximately 45% (HB 293) was recorded. But on the other side, the gray iron had lower tensile strength (Rm = 226 MPa) against average values from other melts.

More than half of the melts were produced with a lower Sc than the specified EN (Sc min. 0.87). The average value of Sc = 0.850 is below this value too. It is possible to expect the opposite result in the production of synthetic gray iron (100% steel scrap).

The average value HB = 201 is optimal for this brand of gray iron even though the dispersion of the values HB (183–225) is relatively high in a whole range of the chemical composition (Sc = 0.798–0.934) (**Figure 6**).

On the base of multiple regressions [15], dependence equations of tensile strength Rm and Brinell Hardness HB on C, Mn, Si, P, S, and Cr were calculated.


*NOTE:* the first line*—arithmetic average,* the second line*—standard deviation,* the third line*—the lowest value of the file,* the fourth line*—the highest value of the file, and n—number of melts.*

#### **Table 1.**

*The statistical results of the chemical composition and the mechanical properties.*

**Figure 5.** *Influence of the degree of saturation on the tensile strength Rm.*

Tensile strength (MPa):

Rm ¼ 340*:*53–17*:*15%C þ 19*:*7%Mn–10*:*68%Si–34*:*23%P þ 10*:*37%S–57*:*76%Cr

(12) correlation coefficient 0.5849. deviation s = 51.922. significance level α = 0.05.

Brinell Hardness HB:

HB ¼ 284*:*21–19*:*3%C–31*:*17%Mn þ 6*:*49%Si–19*:*98%P–11*:*66%S–31*:*08%Cr (13)

correlation coefficient 0.3852. deviation s = 69.118. significance level α = 0.05.

Regression dependence of the chemical composition on tensile strength Rm and Brinell Hardness HB identically show the most significant effect of content C, Mn, and Cr with literature data [16, 17].

The influence of sulfur is interesting, which increases the strength and reduces the hardness in evaluated melts.

The content of phosphorus, normally not evaluated, is significant in evaluated melts—it reduces both tensile strength Rm as well as Brinell Hardness HB.

Besides the standard evaluation of quality for cast iron by tensile strength and hardness eventually by chemical composition, the quality criteria were also evaluated (**Table 2**). It was the criteria that quantitatively represent the effect of particular production conditions on reached cast iron properties in comparison with the optimal statistically valid conditions. Really quality cast iron should show the highest degree of maturity RG and the lowest relative hardness RH.

The quality criteria for cast iron produced from 100% steel scrap rate are shown in **Table 3**. From the quality criteria (**Tables 2** and **3**), it can be stated that produced cast irons show a lower degree of maturity, which means they have lower strength than corresponds with their chemical composition. On the other side, synthetic cast iron shows a high relative hardness that in the final result decreases its quality number.

From the identified quality criteria, it can be concluded that produced gray irons show the average values of quality, while the degree of maturity RG is higher (114.5%) and the relative hardness RH is slightly lower. It is the result of the composition of the charge (without pig iron) as well as the result of low overheating of cast iron (1420– 1440°C), but it is recommended to overheat it above 1480°C (for economic reasons). Despite these results of the quality criteria, it can be concluded that produced gray iron complies with EN.


**Table 2.** *The quality criteria.*


#### **Table 3.**

*The quality criteria of synthetic gray iron.*

**Figure 7.** *Typical microstructure of gray iron of standard melts.*

#### **Figure 8.**

*Microstructure of synthetic gray iron, etched 2% Nital, 500x.*

The microstructure of all melts was pearlitic with a 92–96% portion of pearlite (**Figure 7**). Cementite in the structure of melts was not observed.

In synthetic gray iron (100% steel scrap), there was full pearlitic microstructure and there were detected carbides (**Figure 8**). Attendant of these carbides was the cause of higher hardness in this gray iron.

Besides the significant influence of the chemical composition of gray iron, which is necessary to evaluate more complex, that is, including desirable and undesirable additives—chemical elements and impurities, the quality of cast iron is closely related to the metallurgy of its production. These include the following:


*Evaluation of Metallurgical Quality of Cast Iron Using Quality Criteria DOI: http://dx.doi.org/10.5772/intechopen.107291*

#### • casting temperature.

The highest quality and the most widely used batch material for the smelting of iron is pig iron. Its quality is highly variable; it is linked up with the manufacturer, that is, the conditions of the blast furnace production. Most often, it is contaminated with trace elements and different gas content (N, H, and O), or their compounds (impurities). It is necessary to measure the content of Ti (up to 0.15%), Ca (up to 0.025%), Al (up to 0.004%), and Ni, Cr, Cu, V at its choice.

Besides the common types of foundry and steel industry pig irons, there are now also produced synthetic and semi-synthetic types that are characterized by their specific properties. It is important to check the quality of the new brand (new manufacturer) and to use one type of pig iron for a long time.

Another, particularly cost-effective batch material is steel scrap, and its quality is very diverse. Its use in the greater proportion is currently at smelting in electric furnaces (EIF and also EAF)—up to 100% share in the production of synthetic iron. The properties of such cast iron are significantly different from the properties of cast iron produced from the cupola furnace (max. 30% of steel), respectively; cast iron is produced with a higher proportion of pig iron.

It is necessary to know the quality (purity) of other batch materials, especially scrap iron, reversible material, and various impure iron-containing materials and their impact on the final quality of cast iron. Affordable material is cast iron turnings, without negative effect on the quality of the cast iron, especially the roughing of own castings.

Metallurgical processes and therefore the quality of the resulting cast iron are related to the type of furnace. The most important metallurgical parameters of smelting are temperature of the overheated metal, its standing time after meltingdown, as well as the possibility of some metallurgical processes during smelting (desulfurization, dephosphorization, reduction of gases, etc.). The most extensive metallurgical treatment options are in the electric arc furnace. However, the procedure is more energy demanding.

Today, there are extensive options available (procedures and equipment) for desirable out-of-furnace treatment of liquid cast iron, which not only increases its quality, but also the cost of its production.

The general rule is to keep the lowest temperature of the casting, which is most closely connected with the wall thickness and weight of the cast and with the liquidus temperature of casting cast iron. Low casting temperature positively affects crystallization (formation of macro- and microstructure) and uniformity of characteristics of the cross section of the walls and various parts of the cast iron and, especially, it reduces the tendency to form micro- and macroshrinkages as well as heat stress during solidification.

#### **4. Conclusions**

The production of high-quality cast iron according to EN-GJL-250 (EN 1561) with a lower level of Sc < 1 is possible mainly in the production of thick-walled castings with a guaranteed higher required hardness. Many factors affect the quality of cast iron. Their significance is still being investigated, often with quite unexpected results (sulfur content in gray iron). For an easy assessment of the metallurgical quality evaluated by mechanical properties, statistical methods are used, especially multiple correlation and comparison with the achieved optimal parameters.

Quantitative relationships between chemical composition and tensile strength Rm and hardness HB were determined using statistical methods (multiple correlation regression equations). The following conclusions follow from the results of operational smelting in the foundry:


From the quality criteria, it can be concluded that the produced cast iron shows a lower level of RG; that is, they have lower strength than corresponds to their chemical composition. Synthetic cast iron (100% steel scrap), on the other hand, exhibits high relative hardness, which ultimately lowers its quality number (GZ 56.21).

It is a result of low overheating of cast iron (1420–1440°C); it is recommended to overheat up to 1480°C.

The desired final quality of gray cast iron is closely related to the customer's requirements, as well as to the financial costs of securing it. The difference in costs for the production of up to 100% synthetic LLG is the most current (up to €200/t).

### **Acknowledgements**

This work was supported by the Scientific Grant Agency of The Ministry of Education of the Slovak republic No. KEGA 018TUKE-4/2022, KEGA 004TUKE-4/2023, VEGA 1/0002/22, VEGA 1/0265/21, and APVV-19-0559.

### **Author details**

Peter Futas\* and Alena Pribulova Technical University of Kosice, Kosice, Slovakia

\*Address all correspondence to: peter.futas@tuke.sk

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Evaluation of Metallurgical Quality of Cast Iron Using Quality Criteria DOI: http://dx.doi.org/10.5772/intechopen.107291*

#### **References**

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[2] Ihm M. Introduction to Gray Cast Iron: Brake Rotor Metallurgy. Livonia, Michigan, United States: TRW Automotive; 2013

[3] Collini L, Nicoletto G, Konečná R. Microstructure and mechanical properties of pearlitic gray cast iron. Materials Science and Engineering. 2008;**488**:529-539

[4] Kotus M, Andrassyova Z, Cico P, Fries J, Hrabe P. Analysis of wear resistant weld materials in laboratory conditions. Research in Agricultural Engineering. 2011;**57**:74-78

[5] Modern Casting. 2021. Available from: http://cdn.coverstand.com/55001/ 687958/3ba370da37f7b6c13efcbf97a 5335c779891062b.4.pdf

[6] Futáš P, Pribulova A, Pokusova M, Junakova A. Liatiny—Vlastnosti, výroba, použitie, Košice. 2020

[7] Singh R. Cast iron metallurgy. Materials Performance, Materials Selection & Design. 2009;**9**:58-61

[8] Pereira A, Boehsa L, Guesserb W. The influence of sulfur on the machinability of gray cast iron. Journal of Materials Processing Technology. 2006;**179**:165-171

[9] Kumar B, Singha A. Effect on the mechanical properties of gray cast iron with variation copper and molybdenum as alloying elements. International Journal of Engineering Research & Technology. 2014;**3**:81-84

[10] Baron AA, Palatkina LV. Choice of the optimum criterion for estimating the strength of gray cast iron using the primary structure parameters. Russian Metallurgy. 2021;**5**:1555-6255

[11] Sujana W, Widi KA, Rahardjo T, Prihatmi T, N. The ability of nitrogen atomic absorption in the formation of iron nitride on flake structure and nodule in cast iron. In: Annual Conference on Science and Technology (ANCOSET 2020) IOP Publishing Journal of Physics: Conference Series 1869. Malang, Indonesia: 2021

[12] Abhijit Ramesh Patil PN. Gore: Study of factors affecting tensile strength of gray cast iron. Journal of University of Shanghai for Science and Technology. 2021;**23**(11):759-768

[13] Lian XT, Zhu JN, Dong H, Wang YM, Liu JD. Effects of microalloying elements on microstructure, element distribution and mechanical properties in gray irons. International Journal of Metalcasting. 2020;**14**(4): 1025-1032

[14] Döpp R. Beitrag zur Entwicklung der Eisengussdiagramme. Giesserei Rundschau. 2013;**60**:328-334

[15] Mertler C, Vannatta R, LaVenia K. Advanced and Multivariate Statistical Methods. Routledge, New York: 2021. DOI: 10.4324/9781003047223

[16] Futas P, Pribulova A, Fedorko G, Molnar V. Influence of steel scrap in the charge on the properties of gray iron. ISIJ International. 2017;**57**(2):374-379

[17] Baron AA, Palatkina LV. Relation between the hardness and the strength of gray cast iron with allowance for the structural parameters. Russian Metallurgy (Metally). 2017;**11**:984-988

#### **Chapter 6**

## Refractories for the Cast Iron Melting

*Prasunjit Sengupta*

#### **Abstract**

Refractory is a very important component in economically successful melting of cast iron. Refractory is used to line the furnace or any other vessel used for melting or holding of the molten metal. This chapter has discussed the different type of furnaces used for the melting of cast iron, the special features of those furnaces and the operational parameters of those furnaces with special emphasis on the coreless induction furnace, which is most commonly used. It has dealt with the installation practices of the refractory lining and also has discussed the mode of failure of the refractory lining and the precautions to be taken during installation and during use.

**Keywords:** cupola, induction furnace, quartz, silica, corrosion, buildup, superheating

#### **1. Introduction**

Cast iron is an important engineering material and has numerous applications in Civil Engineering, Architecture, Agriculture, etc. Manufacturing of Cast iron products is comprised of first melting and then casting process, normally followed in Cast iron foundries. Cast iron contains about 2–4% C and 1–2% Si and the melting takes place at a temperature of 1550C. The furnaces used for melting the Cast iron need to be lined internally with Refractory material which can withstand that temperature continuously in presence of molten metal and slag to protect the integrity of the furnace structure. Different type of furnaces can be used for melting the Cast iron and the quality of the Refractory material used depends upon the furnace type. Although the Refractory cost per ton of processed cast iron is not high and significant but the refractory plays a very vital role towards the economic viability of the project.

The Refractory lining influences the furnace operational efficiency and the productivity. Higher is the refractory life, lower is the stoppage time and higher is furnace availability and productivity. Refractory quality influences quality of the castings also, because of the inclusion, coming from refractory. The incorporation of inclusion in the casting impairs its mechanical property and appearance.

We shall discuss here about the different types of furnaces used for the cast iron melting, different types of the Refractories used for different kind of furnaces, installation of refractories and the cause of failure of Refractories.

#### **2. Furnaces used for melting cast iron**

Three types of furnaces are mostly used for the Cast iron melting in the foundries. These are:-


The refractories are designed to withstand the operational conditions and the environment inside the furnace and therefore it is essential to know the furnace and operational details connected to refractory selection.

#### **2.1 Cupola furnace**

The typical Cupola furnace cross sections are shown in **Figure 1** [1].

The cupola is a shaft type cylindrical structure as shown in **Figure 1**. The principle of operation is similar to Blast furnace. The pig iron and scraps, lime stones and coke are charged from the top and air is blown from the bottom when the oxidation of Carbon generates heat which melts the iron and it is collected at the bottom of the furnace from where it is tapped out. The hot air moves upward through the bed exchanging its heat with the downward moving cold burden and preheating it. Two major reactions take place inside the cupola. The first one is the oxidation of carbon in the coke C + O2 = CO2, which is highly exothermic reaction and increases the temperature inside and melts the iron. The molten iron picks up the carbon according to the reaction 3Fe+2CO = Fe3C + CO2 which is an endothermic reaction. Temperature

**Figure 1.** *Cupola furnace.*

inside the Cupola can reach up to 1600C and temperature control is not easy and precise in the Cupola furnace. Cupolas are used mainly where the large volume of Cast iron is melted.

#### **2.2 Arc furnace**

The typical arrangement of Arc furnace is shown in **Figure 2** [1]. This furnace is a cylindrical Refractory lined steel shell fitted with three Carbon electrodes inserted through the Refractory lined roof of the furnace. The scrap and the pig iron and the fluxes are charged through the door inside the furnace and the power is made on. The arc between the charge and the electrodes produces arcs which generates high temperature and melts the charge.

#### **2.3 Induction furnace**

This is the most widely used furnace in the foundry for melting the cast iron because of its easy and precise control of temperature and melt chemistry. The principle of induction furnace is same as a transformer. The electric current is passed through a water cooled coil and when electrically conductive solid metal kept inside the coil, it gets heated up because of induction. Two different types of induction furnaces are there.

#### *2.3.1 Coreless induction furnace*

The coreless induction furnace basically consists of the cylindrical refractory crucible surrounded by the induction coil supported by the transformer yokes (**Figure 3**). The energy is transmitted in such induction furnaces by passing an electric current through the coil which creates a magnetic field. Voltages are induced in the feed material due to this magnetic field, whereby eddy currents are created due to the conductivity of the metal. The induced current heats the charged material in accordance with Joule's law and it melts after a certain heating time.

Any current I, AC or DC, passing through an electrically conducting material causes a voltage drop V resulting in energy conversion to heat. Heat generated in the process is defined by V.I = R.I<sup>2</sup> , where R is the electrical resistance of the current path.

**Figure 2.** *Arc furnace.*

#### **Figure 3.**

*Vertical section of coreless induction furnace.*

The resistance of the current path is inversely proportional to the cross-section area in which the current is flowing.

Coreless induction furnace normally has capacity up to 50 Ton. It can run by the main frequency of 50 Hz or by frequencies 200-1000 Hz called medium frequency furnace. Medium frequency furnaces are mainly used in industries because they have got certain advantages over the main frequency furnaces e.g.,


#### *2.3.2 Channel induction furnace*

Channel induction furnaces are mostly used for holding the molten metal or for superheating the molten metal. It is used along with the Cupola to hold molten metal. The arrangement of the furnace is shown in **Figure 4**.

Power consumption – Theoretically, melting one ton of Cast iron at 1500C should consume 396 Kwh of energy, but in actual practice it takes about 500 Kwh of energy because many types of energy losses takes place which is shown in **Figure 5** [2].

#### **2.4 Comparison of the furnaces**

All the different types of furnaces discussed have some special features, advantages and disadvantages. Selection of the right kind of furnace depends upon the grades of metal to be produced, required melting capacity, availability and cost of raw materials and consumables, cost of electricity and coke, capital investment, operational cost, environmental restrictions, available space etc. Amongst all these different *Refractories for the Cast Iron Melting DOI: http://dx.doi.org/10.5772/intechopen.105973*

**Figure 4.** *Channel induction furnace.*

type of furnace used for Cast Iron melting, most used furnaces are Cupola and Coreless Induction furnace. The comparison of the special features of Cupola and Coreless Induction furnace is shown in **Table 1** [3, 4].


**Table 1.**

*Comparison of features of cupola and induction furnace.*

### **3. Refractory**

Materials are inert inorganic solid materials which can withstand high temperature in contact with solid, liquid and gases to retain its integrity and mechanical strength. These are basically Oxides, Nitrides, Carbides and Borides of Aluminum, Silicon, Alkaline earth metals and transition metals. Selection criteria of refractory for a high temperature process depend mainly upon the following.


5.Thickness of the refractory lining and shell temperature permitted as per design

6.Furnace size and geometry.

7.Economic considerations

Refractory lining has primarily two main functions


#### **3.1 Cupola**

It is to be borne in mind that there is lot of difference between a modern Cupola and the Cupola of earlier days. In earlier days Cupola used to be run for a day and next day it was used to be put down for Refractory maintenance and slag cleaning. Very low quality patching material comprised of sand, burnt brick bats and clay mixture were used for patching purpose. But to-day the modern Cupola is designed for continuous running and therefore high quality Refractories are used to line inside. Cupola is a vertical shaft furnace in which different operational condition exists across its height (zone) and different quality of refractories are used at different zone of the furnace (**Figure 6a**) [5]. The thermal profile across different zone is shown in **Figure 6b** [6].

Charging is done from the top and the uppermost zone experiences heavy mechanical abuse and abrasion by the falling charge material like scrap, limestone and coke and descending burden.

**Figure 6.** *a. Different zones of the cupola furnace. b. the temperature profile inside cupola.*


#### **Table 2.**

*Typical properties of Castables suitable for different zone of cupola.*

Preheating and calcining zone are heated by the upward moving gas and the temperature there is low, below 1000C (**Figure 6b**). High density and low porosity 60–70% Al2O3 refractory bricks or dense low cement Castable can be used here for lining.

In the melting and well zone high quality Al2O3-SiC-C refractory either in brick form or as low cement self- flow Castable is used. Corundum based Castable or bricks can also be used here.

The tuyere is lined with high strength Al2O3-SiC-C or Corundum based low cement Castable. The refractories are degraded mostly by the chemical corrosion by the fluid slag generated in the melting process. The primary condition for the corrosion is the wetting of the refractory surface by the molten slag. The wettability of a solid surface by a liquid happens when the contact angle is low. The addition of Carbon to the refractory increases the contact angle of slag to refractory surface to make it non-wetting and hence more corrosion resistant [7]. The thickness of the lining depends upon the diameter of the Cupola and the intended shell temperature. To maintain low shell temperature and lower refractory thickness the use of insulation refractory is inevitable, otherwise the water cooling of the shell is required.

The use of water cooling leads to energy loss and increases the fuel cost.

Chemical and physical properties of refractory castables used for different zone of the cupola furnace are shown in **Table 2**.

#### **3.2 Coreless induction furnace**

The Refractory issue is much more critical in case of Coreless induction furnace. In Coreless induction furnace the refractory lining separates the molten metal from the electrical copper coil behind (**Figure 3**) through which water is circulated to keep it cool.

The refractory lining thickness is to be optimized taking into consideration of the following:-


*Refractories for the Cast Iron Melting DOI: http://dx.doi.org/10.5772/intechopen.105973*

**Figure 7.** *Effect of refractory lining thickness on electrical efficiency.*

Thinner the lining more is the chance of metal penetration. On the other hand, higher is the refractory lining thickness lesser will be the heat loss through the lining but more will be the loss in electrical energy input given, to heat the charge inside the furnace.

Decreasing refractory thickness improves the coil efficiency but at the same time admits higher thermal losses through the thinner crucible wall. However, since coil losses exceed the thermal losses across the crucible wall nearly by the factor of 10, coil losses play the dominant role here. Taking above all points into consideration high safety margin is eliminated by use of advanced crucible monitoring equipment and the lining thickness is optimized.

The refractory lining thickness commonly maintained is from 75 to 125 mm based on the furnace capacity. The concept of refractory lining design for the induction furnace is quite different from conventional refractory lining.

The main attention is given to arrest crack formation and crack propagation, across the lining thickness, which may pose the danger of penetration of molten metal to strike the coil. During the operation of the furnace the refractory lining always experiences temperature fluctuation and related thermal shock, because the furnace does not run continuously at same temperature. The thermal shock generates crack in the lining, therefore, lining by brick or ramming masses of conventional type are not suitable because in sintered refractory brick, in castable or in a chemically bonded ramming mass, if a crack forms, it propagates very fast.

One of the measures taken to handle this problem is to use the dry powdery mass for lining. The material is designed such that during the use only one third of the lining thickness at the working face will get sintered hard which will withstand the chemical and mechanical abuse of molten metal and charging scrap. The next one

**Figure 8.**

*The thermal profile across the refractory lining thickness in coreless induction furnace (b is total thickness).*

third of the thickness will be in semi-sintered stage and the rest one third of the thickness at the back, in touch with inductor coil, will be in loose form (**Figure 8**) [8]. Under such condition if a crack forms at the working face, it cannot propagate up to the coil and will be arrested in between. The diagram also shows the temperature profile of the lining in case of Quartzite lining (Silica Ramming Mass) which is mostly used in case of Cast iron melting.

The requirements of a ramming mass suitable for the lining of a coreless induction furnace are


#### *3.2.1 Silica ramming mass*

Meets all the criteria mentioned before, to make it a most commonly used lining material for the Coreless induction furnace for melting Cast iron. It is made out of high purity Quartzite or Quartz containing minimum 98.5% SiO2. 0.2–1.5% Boron containing compounds like Boric acid or Boron oxide is used as the sintering aid and mixed with the ramming mass during supply. The percentage of these additives depends upon the operational temperature of the furnace. The grain size distribution in the ramming mass is of utmost importance. The grain size distribution determines its packing density on compaction. Higher is the packing density better will be the performance.

Quartz the main mineral phase in this ramming mass can exist in different crystalline phases and undergoes polymorphic changes at different temperature as shown in **Table 3.**

Due to this polymorphic transformation and associated volume change from Cristobalite to Tridymite the Refractory lining at the middle layer remains tight and does not allow any crack to proceed further and stops any liquid metal penetration. Chemical and physical properties of Silica Ramming mass used for the lining of Induction furnaces are shown in **Table 4.**

#### *3.2.1.1 Installation*

Installation is a very important part towards the efficient running of the furnace. The campaign life of the lining and the electrical efficiency depends upon the quality of the installation. Best quality refractory material will not produce the desired performance unless the installation is sound. **Figure 9** [3] shows how the electrical efficiency is related to the packing density. The aim of good installation is to get maximum and uniform packing density. The process of packing the Refractory mass between the coil and the central former can be done both manually as well as through mechanization. For smaller furnaces below 5 ton capacity manual ramming may be done but for larger furnaces mechanical ramming method must be adopted to ensure best and uniform packing.


#### **Table 3.**

*Polymorphic changes in silica relevant to function of silica ramming Mass.*


#### **Table 4.**

*Properties of typical silica ramming Mass.*

**Figure 9.**

*Relation between the packing density and the energy consumption (MFT-GE/10000/8000KW/250 Hz).*

It is necessary to check, before installation that the ramming mass does not contain any moisture and is perfectly dry. It is very safe to heat the ramming mass before installation to ensure the removal of any moisture. In actual installation process the ramming mass poured on the bottom is first rammed to compact. The ramming material should be poured in such a way that every time sufficient material is poured to get a compacted height of 50 mm and gradually the desired height is build up. The material must not be poured from a height which may segregate the coarse and fine particles of the mass. In case of pouring from a height, a long funnel must be used to ensure no segregation. After the bottom is ready its level is checked and then a mild steel former of the shape, shown in **Figure 10a** is placed on the packed bottom and the annular space between the coil and the former outer wall is packed with the Ramming mass. **Figure 10b** shows some of the tools being used for the compaction of the refractory ramming mass.

Ramming is done dry and therefore is difficult to compact and the tools are also of different design than those used for wet ramming.

Before ramming the inside wall of the coil is plastered with mixture of fine Alumina powder and high Alumina cement mixed with water. The presence of coarse grains may damage the Copper coil. The coating thickness will be 3–5 mm. This provides an extra layer of protection over the coil and also forms a separation layer between the coil and the ramming mass which makes the removal of the used up lining easier after the campaign life of the ramming mass is over.

There is a practice to put some insulation layer like Asbestos sheet over the coil to thermally insulate the coil, but this is not recommended as a correct practice. It consumes both money and time and reduces the lining life by helping sintering front to move towards the coil. This is against the philosophy of the lining design of the coreless induction furnace and moreover Asbestos creates health hazard.

After completion of lining, the scrap is charged inside and the power is put on. The steel former used for the lining is allowed to melt in the process of sintering the lining.

**Figure 10.** *a. Steel former. b. Ramming tools.*

There are methods in which the steel former can be taken out after the ramming is over and before the power is made on. This process is much more economical because the same former can be used number of times and it saves the cost of the former. For removing the former before melting, special binder is added in the ramming mass and the former is heated up to 400C by gas burner inside when the ramming mass, in contact with it, forms a hard layer and enables the pull out of the former which has a taper design to facilitate the removal.

The first heat is very important because it is to be done with care to sinter and stabilize the lining and next heat onwards it can be run in normal routine way. It is also recommended to use clean and good quality scrap in first few heats. The former used for the lining is allowed to melt in service and it actually holds the dry material till it sinters and acquires strength to stand on its own.

After a new lining is constructed, its first heat up procedure is very important. A special heat up schedule is followed which helps in stabilization of the Refractory lining. This is called sintering cycle and should be followed as per the instruction of the supplier of the lining material because it depends upon the grain size distribution, raw material character, quality and quantity of the sintering aid used and also upon the furnace capacity. The most common sintering aid is Boric acid or Boron Oxide used for Silica Ramming mass. **Table 5** shows the typical heat up schedule used for a certain ramming product.

After rising, the temperature is hold at a certain temperature, called sintering temperature, which depends upon the quantity of additive used. **Table 6** shows the relation between the kind of sintering aid used, its percentage and the sintering temperature.

#### *3.2.1.2 Mechanism of refractory degradation*

Refractory lining life depends not upon quality of the refractory alone but more upon the other parameters e.g., furnace size, quality of installation and the


#### **Table 5.**

*Heat up schedule of the coreless induction furnace.*


#### **Table 6.**

*Typical relation between additive% and sintering temperature.*

deviations from SOP etc. Same Refractory performs differently in different cast iron melting units.

Following are the major causes of refractory degradation process takes place in induction furnace.

1.Chemical corrosion and erosion

2.Crack formation

3.Erosion

4. Superheating

5.Build up

#### *3.2.1.2.1 Chemical corrosion and erosion*

It causes the gradual loss of the lining thickness due to the chemical reaction of the refractory material with the charge material or alloying elements in the metal. The presence of carbon and other oxides like Mn, Mg, and Al present in the melt reacts with SiO2 and reduces it following the reaction as below.

$$\text{2X} + \text{SiO2} = \text{2XO} + \text{Si} \tag{1}$$

The content of the said impurities must be low to avoid the chemical corrosion. Carbon in Cast iron also attacks SiO2 at a temperature above 1450C to 1480C when the boiling process sets in. The FeO present in the slag reacts with SiO2 to form low melting compound Fayalite (2FeO.SiO2) having melting point 1180C and corrodes SiO2 Refractory lining. Slag also contains Manganese silicate (MnO.SiO2) with 1250°C as its melting temperature. Both of these compounds occur in the slag in proportion 10 to 30% and 2 to 10% respectively. Input of rusty scrap makes the situation worse.

The content of the said impurities must be low to avoid the chemical corrosion. Carbon in Cast iron also attacks SiO2 at a temperature above 1450C to 1480C when the boiling process sets in.

During the charging of the scrap in molten metal or during the CO boiling process, molten metal is splashed on the refractory lining and later gets oxidized and forms FeO and then to Fayalite.

When the metal is hold in the furnace for longer time metal gets oxidized to FeO and causes the erosion in the lower part of the crucible. During holding, the temperature of the molten metal should be kept as low as possible to retard the oxidation process and generation of FeO. In melting of nodular iron, SiO2-Al2O3-MgO eutectic is formed at 1365C [9] and the lining gets eroded because if it's higher tapping temperature.

If the scrap, used as feed to furnace, contains Zn, then it vaporizes beyond 900 C and permeates through the lining material and condenses on the inductor coil. This deposited Zn layer may cause arc formation in the inductor coil and damages it [8]. To avoid this problem the initial three charges must be free from any Zn and the lining is allowed to sinter and get dense to retard the permeation of Zn vapor. The same is applicable during the charges after cold heat because the time is to be allowed to heal up the cooling crack through which the vapor permeates easily. A high temperature gradient from hot to cold face of the lining is also recommended to allow the condensation zone away from the coil. The coil coating material with high thermal conductivity is recommended.

The CO gas also permeates through the lining and gets converted to C and CO2 as per the Boudouard reaction

$$\text{'} \mathbf{2CO} = \mathbf{CO2} + \mathbf{C} \tag{2}$$

This Carbon gets deposited on the coil. Beside this, Sulfur vapor generated from the MgS in recycled nodular iron also penetrates through the lining and reacts with the Oxygen and the moisture in the lining to form Sulfuric acid as per the reaction

$$\text{H}\_2 + \text{3O}\_2 + \text{2H}\_2\text{O} = \text{2H}\_2\text{SO}\_4\tag{3}$$

Sulfuric acid attacks the Copper coil to form Copper Sulfate and damages the coil.

#### *3.2.1.2.2 Crack formation*

in the lining is inevitable because of thermo-mechanical stresses developed in heating and cooling of the lining and due to volumetric changes during the polymorphic transitions of Quartz. But formation of deep crack is dangerous which may allow the passage of molten metal through it to strike the coil. Formation of small cracks is not a concern rather formation of smaller cracks absorbs the stress and does not allow the formation of bigger cracks. Cracks can be of different type and the reason of their formation is shown in **Figure 11** [10].

The lamination is formed due to separation of two layers during compaction of the lining and care must be taken to avoid such layer formation. The vertical cracks are

#### **Figure 11.** *Different types of lining cracks and their causes.*

formed during over sintering also and care must be taken to reduce the amount of sintering agent in such case. Crack also formed if the density is not uniform throughout the lining. Segregation of the material can also cause such non uniformity. To avoid segregation the refractory material must not be poured from much height or to pour the material through a long funnel during lining.

#### *3.2.1.2.3 Erosion*

Erosion is more of a physical process and aggravates chemical corrosion by exposing the fresh surface available for chemical reaction and corrosion. Erosion is connected to the extent of turbulence of the bath of molten metal. Higher the turbulence more is the erosion.

The characteristic of induction melting is that the bath is in constant movement, which is called inductive stirring. The amount of stirring is determined by the size of the furnace, the power put into the metal, the frequency of the electromagnetic field and the type/amount of metal in the furnace.

When a furnace is operated at a frequency lower than ideal, the result may be a violent stirring action that may produce inclusions of slag and refractory particles. Metal loss may be excessive due to excess surface area of the melt and oxidation of volatiles.

In many cases the refractory lining life is reduced because of using too low of a frequency to produce strong stirring. On the other hand, if too high a frequency is selected for the size of the furnace, there may be a complete lack of stirring, uneven heating throughout the charge, excessive side-wall temperatures and difficulty in attaining homogeneous melts.

The degree of agitation in molten metal can be indicated by Stirring Index, which is defined as [11].

$$\text{SI} = \frac{6000 \sqrt{\text{KW} \cdot \frac{\text{D}}{\text{SG.f.} \rho}}}{A} \tag{4}$$

**Figure 12.** *Relation between the furnace size and the ideal frequency of operation.*

Where, SI- Stirring Index, KW = Power of Furnace in KWh, D = Melt diameter, SG = Sp. Gravity of metal, ρ = Metal resistivity, f = Frequency, A = Cross sectional area of the melt (πD<sup>2</sup> /4). Relation between furnace size and frequency is shown in **Figure 12** [12].

Due to erosion when the lining gets thinner, the furnace draws more power and the melting rate becomes faster and this is an indicator of lining erosion. Data in **Table 7** [2] illustrates this effect in a 3 ton capacity furnace of 700 KW rating.

#### *3.2.1.2.4 Buildup*

When the slag makes contact with the refractory lining of a furnace wall (or other areas of the holding vessel) that is colder than the melting point of the slag, the slag is cooled below its freezing point and adheres to the refractory furnace wall or inductor channel. The source of these build up material are the oxides from the oxidation of the metal or contaminants charged into the furnace e.g. molding sands. Buildup normally occurs in the areas where the flow or the turbulence is minimum. Some of the major mineral forms found in the buildup, are shown in **Table 8** [13].

The buildup gradually reduces the working volume of the furnace and forced to take shutdown for the new lining. The remedy is to use the better quality of scrap with lesser contaminants. Sometimes the use of flux reduces the build up by reacting with it to reduce the melting point so it goes into the slag.


**Table 7.**

*Effect of refractory lining age on energy consumption.*

#### *3.2.1.2.5 Superheating*

The generation of localized heat, which leads to high temperature at some spots, is very detrimental for the refractory lining and may cause lining failure. The major reasons for the localized superheating of the lining are shown in **Figure 13** [10].

During the scrap charging in the furnace, it may so happen that some scraps remain at hanging position at the top while the liquid metal is formed below and an air gap forms in between the liquid metal at the bottom and the charge at the top in hanging position and is called Bridging. This is a very dangerous situation for the refractory because the liquid metal below will be superheated and will have high stirring effect due to high power density and lesser quantity of molten metal. The metal temperature can shoot up above the melting point of refractory and erosion will be high because of strong agitation of molten metal. Under such condition the refractory lining can give way and molten metal can penetrate through the lining to strike the water cooled coil causing severe explosion (**Table 8**).

Once the bridging of scrap happens the power must be switched off immediately. The scrap sizes are very important to control the bridging and the charges must be of different sizes.

The trapped metal pieces inside the refractory lining can also cause the local superheating of the refractory lining. The penetrated metal fin inside the lining can also cause the superheating of the lining.

#### **Figure 13.**

*Factors that cause superheating of molten cast iron.*


#### **Table 8.**

*Some minerals, found in the buildup material in cast iron melting.*

#### **3.3 Transport of molten metal**

For transportation of the molten cast iron in foundries Ladles can be used and these ladles can also be lined with Silica Ramming mass in similar way as it is being done for induction furnace. The advantage of Silica Ramming mass is its low cost and lower drop in metal temperature because of its low thermal conductivity. Smaller foundry ladles also use sol-gel castable lining which is amenable for fast drying and heat up.

In case of cupola also, the liquid metal can be transported through ladle lined by Silica Ramming mass which is most economical. In case of bigger ladle Alumina—Silicon Carbide bricks can be used which gives better campaign life but it is having much higher thermal conductivity and need insulation at the back to prevent the heat loss.

#### **4. Concluding remarks**

The driving force acting on industries, in general, today are related to economy, environment and safety and health issues and that brings the changes in current practices. The cast iron industry is not an exception to that.

For example, so far Boron compounds are being used as the sintering aid to Silica Ramming mass, but Boron compounds are found to have detrimental effects on human health. Trials are on the way to develop Boron free Silica Ramming masses and initial trial results are very encouraging.

New methods for melting, like Electron beam melting, Microwave melting, Solar furnaces [13] are under trial and Refractory requirements will be changed along with the changed furnace type in future.

#### **Author details**

Prasunjit Sengupta SKG Refractories Ltd, Nagpur, India

\*Address all correspondence to: pseng4311@gmail.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

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[2] Medias J. Efficient Melting of Coreless Induction Furnace – Good Practice, by Energy Efficiency Enquiry Bureau. Harwell, Didcot, Oxfordshire: ETSU. Argentina, UK. 2000

[3] Schmitz W, Trauzeddel D. The Melting, Holding and Pouring Process-Energy and Process Related Aspects. Germany: Otto Junker GmbH; 2010

[4] Medias J. Alternatives for Hot Metal Production: Cupola, Induction and Arc Furnace. Buenos Aires, Argentina: Jorge Medias; 2010

[5] Eliott R. Cast Iron Technology. Somerset, England: Butterworth & Co. (Publishers) Ltd. 1988. p. 47

[6] Takahashi T. Refractories Handbook. Japan: The technical association of Refractories; 1998

[7] Khanna R, Ekram-ul-Haq M, Sahajwalla V. Chapter-10: Influence of wettability and reactivity on the degradation-interaction of molten iron and slag with steelmaking refractories at 1550C-R. In: Wetting and Wettability. London, UK: Intech Open; 2015. DOI: 10.5772/61271

[8] Kukartsev VA, Kukartsev VV, Tynchenko VS. Causes of quartzite lining destruction during operation of the IChT furnace and the ways to prevent them. In: IOP Conf. Series: Earth and Environmental Science. UK: IOP Publisher; Vol. 459. 2020. p. 062090

[9] Dotsch E. Refractory demands on inductive melting of cast iron. Baden-Baden, Germany: Refractories Worldforum; 2011. p. 3

[10] A trouble shooting guide to Silica Dry Ram Refractories-M/S Allied Refractories, Columbia, USA, 60th Indian Foundry Congress Souvenir

[11] Prabhu S. Metal Stirring in Coreless Induction Furnace. Foundry Management and Technology; OH, USA. 2018

[12] Selecting the right unit for the efficient induction melting – Michael Fanz Huster, USA: Foundry Management and Technology; 2021

[13] Mechanism and Control of Buildup Phenomenon in Channel Induction and Pressure Pouring Furnace-Part 1, David C Williams and R.L.(Rod) Naro. Ohio, USA: Ductile Iron; 2007;**1**:44-55. Available from: https://www.asi-alloys. com/pdf/Buildup%20%20Phenomenon %20in%20Channel%20furnaces%20DIS %202007.pdf

### *Edited by Swamini Chopra and Thoguluva Vijayaram*

*Extraction Metallurgy - New Perspectives* explores the dynamic world of metallurgical processes and materials extraction. This volume offers fresh insight into the latest and cutting-edge research that will help both new learners and seasoned professionals. Authored by distinguished metallurgists and researchers, this book sheds light on the intricacies of metallurgical processes and their real-world applications, innovative approaches and methodologies that are reshaping the metallurgical landscape, and global perspectives on extraction metallurgy, presenting diverse case studies and examples from across the world. Written with the needs of researchers and non-native English speakers in mind, the book employs clear and concise language, making complex topics accessible to a wide audience. *Extraction Metallurgy - New Perspectives* is a must-read for students, academics, and professionals engaged in metallurgical research and industrial applications.

Published in London, UK © 2024 IntechOpen © abadonian / iStock

Extraction Metallurgy - New Perspectives

Extraction Metallurgy

New Perspectives

*Edited by Swamini Chopra* 

*and Thoguluva Vijayaram*